Patent GB-1065834-A (GB)
Title: Device for transmitting signals
Inventor: GRACHEV BORIS ALEXANDROVICH
IPC: E21B47/12
Filed: 1964-01-15
Abstract: 1,065,834. Transistor gating circuits; pulse modulation systems. VSESOJUZNY NAUCHNO-ISSLEDOVATELSKY I PROEKTNOKONSTRUKTORSKY INSTITUTE KOMPLEKSNOI AVTOMATIZATSII NEFTJANOI I GAZOVOI PROMYSHIENNOSTI. March 25, 1964 [Jan. 15, 1964], No. 1749/64. Headings H3T and H4L. [Also in Divisions G1 and G3] The speed of rotation of an earth drill is measured by the frequency of the A.C. output of a tachogenerator coupled to the drill, which is transmitted in bursts whose mark and space times represent two auxiliary parameters of the drilling process. As shown (Fig. 1), the output from transducer 4, measuring the end thrust of the drill, and transducer 5, measuring the electrical conductivity of the earth strata, are converted to voltage magnitudes at 6, 7, determining the on-off times of a bi-stable circuit 8 controlling a switch 3 in series with the output from A.C. tachogenerator 1 coupled to the drill. The tachometer output voltage is stabilized by a unit 9 (Fig. 5) assisted by a non linear resistor R connected in parallel, whose resistance decreases with increase of voltage, and rectified, to provide the D.C. voltage for the circuit transistors. Transducer 4 comprises a transformer whose interwinding coupling is varied by a non-magnetic gap controlled by the end thrust of the drill. The primary winding I of the transformer is fed with A.C from a multivibrator 17. The output signal from the secondary winding II is amplified at 19 and rectified at 20. Initially transistor Q4 is non- conducting, Q5 is conducting and Q6 is non- conducting, presenting a high impedance across the primary winding of transformer T2, allowing half-wave signals from tachometer 1 to pass through diodes D1, D2 and transistor Q1, Q2 to an output circuit. Capacitor C1 is charging through resistor R4 and the base of transistor Q7 until its voltage is equal to the rectified signal voltage from transducer 4 stored in rectifier 20, when diode D3 becomes conductive and charging ceases. This causes Q7 to become blocked, opens Q8 and reverses the conditions of subsequent transistors Q4, Q5 and Q6, so that the latter, in its conducting state, forms a low impedance shunt across transformer T2 and suppresses the tachometer signal voltage from transmission. Thus the transmitted pulse duration is determined by the value of the end thrust as indicated by the rectified voltage stored in 20. Capacitor C1 now discharges through diodes D4, D5 and transistor C4. When Q6 conducts, at the end of the pulse period, a voltage representing the resistance of the material surrounding the earth drill, obtained across electrodes 21, 22, is fed through filter 23, amplifier 24 and rectifier 25 to determine the charging time of capacitor C2. When the voltage across C2 equals the rectified signal voltage C2 discharges, Q6 is blocked, and the tachometer signal is again transmitted. Thus the gap in the transmitted signal is determined by the value of the earth resistance as indicated by the rectified voltage stored in 25. The mark and space times are preferably shown directly on a log scale chart.